Ignitron starter circuit



Nov. 26, 1940. H. KLEMPERER 29222952@ GNITRON STARTER CIRCUIT FiledMalch 23, 1939 Zn veut o1 glia/V7' ww UWT-*- HW. @www BLEEDl-P any D/SKRsaT/F/egs Patented Nov. 26, 1940 UNITED STATES IGNITRON STARTER.CIRCUIT Hans Klemperer, Belmont, Mass.

Application March 23,

12 Claims.

The present invention relates to ignitron starter circuits and to meansand methods of eliminating such auxiliary tubes as the thyratrons or themercury type tubes.

In the usual system in which ignitronswere used, a thyratron or otherauxiliary tube was used in series in the circuit of the starter elec;trode since the ignitron starter could not readily withstand a reversecurrent. This also is the l-l reason why the ordinary peakingtransformer could not be used successfully because of the dimcultlesoffered by the negative peak. A thyratron used in this way has a veryshort life, and

is therefore both expensive and inconvenient. l The shortness of life ofthe tube is due to the necessity of a very high peak current required bythe starter and the sharpness of the impulse which does not allow thethyratron cathode to adjust itself in time and therefore the life of thetube is very short unless an excessively large and therefore expensivetube is used. A mercury pool type auxiliary tube is also too expensiveand costly to operate since it is necessary to install holding arcs andmechanical starting f means in the auxiliary tube.

'I'he means and-'method of the present invention eliminate the use ofauxiliary tubes in the operation of ignitrons. By the present inventionthe necessary magnitude and wave form of current and voltage aresupplied to the ignitron starting electrode through the use of iron corecoils and circuits connected to the ignitron starting electrode andindependently energized by both direct and alternating current sources.ref. In the operation of ignitron tubes, the optimum operating conditionis obtained as far as the functioning of the starting electrode isconcerned,

if its action brings about a discharge of the tube by its momentaryoperation and then remains dormant, using no power until the tube isagain to be discharged.

It must be appreciated that in the present invention, the action andoperation of the starting electrode occur only during a very shortinterval as compared with the time of flow of current in the tube, andthat no auxiliary means are necessary to cut the starter current afterthe main anode has picked up.

The circuit and means used in the present l invention have this aim inview and not only is there provided a sharp peaked current to thestarting electrode at the desired moments, but between these moments,the current and therefore the power consumed by the starting electrodeare practically zero. In accomplishing the 1939. .Serial No. 263,735

results of the present invention, no gaseous or vacuum tubes arenecessary, and what little direct current is needed may be supplied froma dry disk rectifier, for instance, a copper oxide rectifier, shunted bya condenser, and controlled by a rheostat or by a transformer havingseveral taps as will appear later.

The advantages and merits of the present invention will be more clearlyunderstood from the description of the apparatus given below ernbodyingthe invention, when taken in connection with the drawing hereto annexed,in which:

Figure l shows a schematic wiring diagram with the ignitron controlledin accordance with the principles of the present invention;

Figure 2 shows a complete schematic wiring diagram as applied to a threephase system;

Figure 3A shows a schematic diagram of the starter electrode circuit;

Figures 3A, 3B, 3C, 3D and 3E show a group cf curves as applied to thefunctioning of the starter electrode in Figure 3A;

Figure 4 shows modifications for by-passing reverse current; and

Figure 5 shows a means for checking the adjustment of the direct currentsupply.

With reference to Figure 1, the ignitron tube i I has the usual cathodepool 3, anode 4, and starter electrode 5. The cathode and anode haveimpressed upon them the alternating voltage of the A. C. source 6through the transformer 2. In accordance with the present invention. thestarter electrode 5 is connected in series with the coil 'l surroundingan 'iron core 8 saturated by the impression upon the coil of the desiredand selected alternating and direct current components. For this purposea transformer 9 energized from the alternating current power source 6 isprovided withl two secondary windings I0 and II, the winding III beingconnected in series with Ithe coil 1 and a condenser I2, which in turnis connected to the cathode 3 of the ignitron tube I. The winding IIserves to supply energy i'or energizing the rectifier I3, which ispreferably of the dry disc type of rectifier and which needs to supplyonly a comparatively small current. The output of the rectifier isconnected across the condenser I 2, preferably with an adjustableresistor Il in series with it to regulate the current drawn from therectifier, the positive side of the rectifier being connected to thestarter electrode side and the negative side of the rectifier beingconnected to the cathode side of the ignitron tube. The output of theignitron may be used in any desired Way as indicated by the D. C. loadI5 and may be controlled by any external means of control, such as byshort-circuiting as shown by the switch control I6. The presentinvention relates particularly to the starter operation and control,which will be discussed at greater length later.

In Figure 1 the control is illustrated as applied to a single-phase A.C. source, the ignitron I serving as one half wave rectifier and theignitron II serving as the other half Wave rectifier; that is, when thecurrent in the transformer 2 is flowing to make the anode 4 positivewith respect to the cathode 3, the ignitron I will operate, and when thecurrent is flowing in the opposite direction, the ignitron I1 willoperate.

In Figure 2 the present invention is applied to a six-phase system.

In the arrangement shown in Figure 2, there is shown a six-phaseconnection for an ignitron control circuit. In this circuit the primaryof the transformer T is connected in A to the three phase A. C. supplywith the secondaries connected in two three-phase Y's, displaced inphase 60 from each other and with an interphase reactor P having itsmid-tap connected to the negative side of the D. C. line. In this waythe two sets of Y branches I, 2, 3, and 4, 5, 6, form six phases, 60apart, each of which is connected to separate ignitrons I1, Iz, Ia, I4,I5, and le, respectively. Each of these ignitrons has separate startingelectrodes S1, Si, Sn, S4, S5 and SG, connected each in series withsaturation coils L1, L2, La, L4, Ls and Le, respectively, correspondingto the coil I of Figure 1, and the proper corresponding alternatingcurrent component of the transformer Tz, namely, l, 2, 3, 4, 5 and 6 ofT2, supplying the positive current peak as indicated in Figures 3A-3E,explained below,

The direct current component is supplied through the transformer windingT3 and the rectifier R, operated by it. In this circuit may be acondenser C corresponding to the condenser I2 of Figure 1 and anadjustable resistance r for proper control and operation of the currentsupplied to the rectifier R. While a six-phase transformer T2 can beused for supplying the A. C.

component for the starter electrodes, a six-phase phase shifter devicecould also be used.

A simplified arrangement of the elements of the present invention isshown in Figure 3A and curves in Figures 3B, 3C, 3D, and 3E illustratethe corresponding values of flux, current and voltage in the starting of`the discharge to the starter electrode and its subsequent status untilthe next discharge occurs.

If pure A. C. were applied to the coil 1, a positive and negative peakwould appear in the current wave as shown in Figure 3C. To suppress thenegative peak 30, a D. C. E. M. F. is added to the A. C. E. M. F. bymeans of the rectifier I 3, Figure 1. This suppresses the negative peak30 and also sharpens the positive peak, Figure 3D, resulting in acurrent curve as indicated by 3|, Figure 3D, which is due to theincreased magnitude of magnetic fiux on the positive side of the curveVthrough the addition of the D. C. current component flowing in the coll1.

plied to the coil becomes very small during that portion of the ux curvethat shows no saturation. During the portion of the curve Figure 3D,

other hand increases rapidly to the sharp positive peak shown by 3I inFigure 3D. Moreover the D. C. current which is sent through the coil(and the starter) in order -to distort the magnetic ux, as describedabove, is given such a polarity and magnitude as to counterbalanceremaining current.

This positive peak flows through the ignitor and, by reaching thecritical current or voltage value, causes a discharge to develop tweenthe mercury surface and the ignitor rod, as indicated in Figure 3E. Theignitor has an ohmic resistance which varies with voltage andtemperature. This varying resistance is responsible for a slightdistortion of the current wave (Figures 3D and 3E), but nevertheless,the ignitor operates according to the principle described.

Generally speaking, about 500 instantaneous watts are needed to cause anarc to pick up at the ignitor tip. After this short interval of powerconsumption, about 5 amperes at about 10 to 20 volt arc drop are neededto keep the arc burning, which power usually is supplied by the externalpower circuit. During this operating period of the ignitron, the ignitorcurrent should be as near to zero as possible in order to avoid heatingof the ignitor tip. In regular ignitor circuits having a thyratron tube,the interruption of the ignitor current, after pickup, is effected byextinguishing the thyratron; i. e, by lowering its voltage below the arcdrop limit. At the corresponding time in the described circuit, afterthe current peak is over, the opposite polarity of D. C. and A. C.currents (Figure 3D) makes the remaining small current between the peakspractically equal to zero. Means of further reduction of that residualin-between current are described below.

The A. C. fiux density in the saturated coil should be designed andafterwards adiusted to obtain minimum currentin between peaks.

-After the coil has been installed an adjustment in the D. C. supplyvoltage may be necessary in order to obtain minimum reverse current withindividually different igni-tors. Such adjustment may be checked with acathode-ray oscillograph, or, if this is not convenient, the dry disc(rectox) operated instrument circuit of Figure 5 is recommended. 'I'hiscircuit is capable of measuring small negative current in the presenceof very large positive current. T'he instrument 40 and rectiflers 4I and42 will pass the reverse current, but block the positive current,measuring thereby only the small negative current.

Instead of individual adjustment, any residual reverse current can alsobe diverted from the starter rod itself by means of the circuit shown inFigure 4, which shows one copper oxide rectifier 43 connected in seriesand one connected in shunt 44 with the starter rod. If the samesaturated coil `I with D. C. bias is employed, the advantage is that onecopper oxide rectifier carries but little current and the otherrectifier has to withstand but little inverse voltage. This is betterthan with normal peaking transformers which generate a large negativepeak of current to be carried by the bleeder rectifier 44, in additionto the large inverse voltage on the bleeder rectifier 44 due to starterrod resistance on the positive peak. In the new circuit of Figure 4, therectifier in series with the starter rod is not subjected to largeinverse voltage, and this is the only rectifier carrying the peakcurrent.

aaaaeao Variation of voltage of the A. C. mains is not harmful with thenew circuits. The negligible in-between" current changes, but no dangerwould occur until the iron became saturated .in

the negative direction also. This would require however, a very highovervoltage on the A. C. mains. The driving power or positive peakvaries about proportionally to the A C. main voltage. Such ordinaryvariations are not harmful to the ignitor operation.l

Time is required to build up the D. C. excitation in this circuit. Rapidcontrol requires, thereu fore, that the ignitor be short-circuited bythe switch I6 shown in Figure 1 so that the current is not interrupted.Gradual control can be obtained by phase-shift of the A. C. supply tothis control circuit. The A. C. supply of the circuit must have lowimpedance to avoid dulling of the peak current wave. For the samereason, windings 35 and lll of Figure 1 should have low magnetic leakagebetween them.

The independent E. M. F. supply is characteristic of this circuit ascontrasted with tube circuits fed from the anode, so that startingcurrent will transfer and burn as an arc between the mercury pool andthe holder of the starter 5, as shown on the Wave of Figure 3E. For thisreason an arcing horn or cap can be provided to take this arc and shieldthe lead-in and other delicate parts. It is also possible to useauxiliary anodes. These recommendations are'not peculiar to thiscircuit, and really represent the construc tion of high voltageignitrons, wheredue to highvoltages on the anode, the ignitor circuit isgenerally electrically independent.

Special alloys, such as permalloy, may be useful for the saturated coil.Common silicon steel was used however with good results.

Having now described my invention, I claim:

1. A circuit for starter operation of an ignitron having cathode, anodeand starter electrodes having, in series with the said starterelectrode, a coil with a magnetic core designed to become saturated uponthe application of normal potentials thereto for supplying a startingpeak of current to the starter electrode on the positive half cycle ofthe potential supplied to the anode, and means for supplying a directcurrent component in series with said coil and between cathode andstarter electrodes for suppressing the negative peak that normally wouldotherwise be created by said coil.

2. A circuit for starter operation of an ignitron having cathode, anodeand starterv electrodes having, in series with said starter, means forsup plying a single-sided peak of current only during the positive halfcycle of the applied alternating current potential to said anode,comprising a coil with a saturable magnetic core connected to saidstarter electrode and energized by direct current and alternatingcurrent components from separate sources.

3. A circuit for starter operation of an ignitron having cathode, anodeand starterl electrodes having, in series with said starter, means forsupplying a single-sided peak of current only during the positive halfcycle of the applied alterA nating current potential to said anode,including means for supplying an alternating current component to saidcircuit from one source and means for supplying a direct currentcomponent to said circuit from another source of such a polarity that itsubstantially suppresses the reverse current that normally wouldotherwise ow in the starter electrode during the reverse hall cycle ofthe alternating current potential supplied to said anode.

4. A circuit starter for operation of an ignitron having cathode, anodeand starter electrodes having, in series with said starter, means forsupplying a single-sided peak of current only during the positive halfcycle of the applied alternating current potential to said anode,including a saturable magnetic core coil connected in series with thestarter electrode, means for supplying a direct current component tosaid coil from one source, and means for supplying an alternatingcurrent component to said starterelectrode in series with said coil fromanother source, and a condenser shunted across said direct current sup-Ply.

5. In combination with a polyphase supply system having an ignitron withcathode, anode and starter electrodes for each supply phase, individualsaturable magnetic core coils in series with each starter electrode,means for supplying an alternating component of the desired phase foreach coil from a suitable source, and a separate single source of directcurrent supplying neutralizing current to said coils for suppressing thereverse current in each starter and peaking the alternating current peakfor each phase.

6. In combination with a polyphase supply system having an ignitron withcathode, anode and starter electrodes for each supply phase, in"dividual saturable magnetic core coils in series with each starterelectrode, means for supplying an alternating component oi the desiredphase for each coil from a suitable source, a separate single source ofdirect current supplying neutral izing current to said coils foreliminating the reverse current in each starter and peaking thealternating current peak for each phase, and a single condenser shuntedacross the direct current supply.

7. In combination with a polyphase supply system having an. ignitronwith cathode, anode and starter electrodes for each supply phase,individual saturable magnetic core coils in series with each starterelectrode, a phase shifter device for supplying an alternating currentcomponent oi the desired phase to each starter, and a separate singlesource of direct current supplying neutralizing current to said coilsfor eliminating the reverse current in each starter and polarizing thealternating current peak for each phase.

8. A starter circuit for operation of an ignitron having cathode, anodeand starter electrodes having, in series with said starter, means forsupplying a single-sided peak of current only during the positive halfcycle of the applied alternating current potential to said anode,including a saturable magnetic core coil connected in series with thestarter electrode, means for supplying a direct current component tosaid coil from one source and means for supplying an alternatingcomponent to said starter electrode in series with said coil fromanother source, a condenser shunted across said direct current supply,and means for adjusting the magnitude of said direct current component.

9. In a system of the type described, having an ignitron with cathode,anode and starter electrodes having, in series with said starter, meansfor supplying a single-sided peak of current only during the positivehalf cycle of the applied alternating. current potential to said anode,comprising a coil with a saturable magnetic core connected to saidstarter electrode and energized by direct current and alternatingcurrent-components from separate sources, and `means shunted directlyfrom the starter electrode to the cath e for further suppressing andby-passing the r verse current that would otherwise ilow through saidcoil.

i0. In a system o! the type described having an ignitron with cathode,anode and starter electrodes having, in series with said starter, meansfor supplying a single-sided peak o! current only during the positivehalf cycle of the applied alternating current potential to said anode,comprising a coil with a saturable magnetic core connected to saidstarter electrode and energized by direct current and alternatingcurrent components from separate sources, and individual rectiiyingmeans in series with the starter electrode and next to it arranged insuch polarity ior suppressing the reverse current nowing through thestarter.

11. A circuit for starter .operation of an electrical gaseous dischargedevice, including cathode. anode and starter electrodes, having inseries with the starter electrode a coil with a saturable magnetic corefor supplying a starting peak o! Vcurrent to the starter electrodeduring the posiassaeao tive halt cycle o! a potential supplied to theanode, means for supplying through said coil to said core an alternatingcurrent component ot magnetomotive force from a source, and means f forsupplying to said core a direct current component of magnetomotive forcefrom another source, said direct current and alternating curf rentcomponents o! magnetomotive force being o! such relative magnitudes thatthe starting peaks oi current supplied to said starter electrode aresubstantially unidirectional.

l2. A circuit for starter operation oi' an electrical gaseous dischargedevice, including cathode, anode and starter electrodes, having inseries with the starter electrode a coil with a saturable magnetic'corefor supplying a starting peak of current to the starter electrode duringthe positive half cycle of a potential supplied to the anode. means forsupplying through said coil to said core an alternating currentcomponent of magnetomotive torce from a source, and means for supplyingto said core a direct current component ot magnetoxnotive force fromanother source.

HANS KIEMPERER.

